The present invention relates to a system for wrapping and securing a plastic film wrap about a package. More specifically, the invention relates to an apparatus and method for heat sealing a film wrapper to secure the plastic film about the package, and further, to retain the separated or tail-end in position for subsequent wrapping operations.
There are known techniques available for wrapping packages on pallets with plastic film or plastic netting in various configurations. When the package wrapping is complete, the wrapper is secured to underlying layers of the wrapping film or, alternatively, to the package-bearing pallet. In known apparatus securing is provided by roping the film, that is, constraining the film to a rope-like shape and stapling the roped ends together, as described in U.S. Pat. No. 4,418,510-Lancaster.
U.S. Pat. No. 4,432,185 to Geisinger provided an anvil for determining the position of the package or load to permit other operating mechanisms to be brought into position for clamping, securing by stapling, and cutting the film. These latter elements were mounted on a separate carriage, which moved into a specific relationship with an anvil by sensing the position of the anvil and thus the site of the package to be wrapped. These earlier systems did not utilize heat sealing to secure the film ends.
In U.S. Pat. No. 4,619,102 to Geisinger, a load on a rotating pallet or platform is wrapped by a plastic stretch film. The stretching apparatus and wrapping means are generally positioned on a stationary platform displaced from the vertical plane of the rotating arrangement. The platform further includes a clamp assembly and sealing apparatus for rotating with the load. After initiation of the wrapping cycle, particularly by a first wrap secured about the package, an anvil is brought into contact with the charge and thereafter the wrapping operation commences. A clamp holding the end of the film is released after the film is sufficiently wrapped to retain itself against the charge. After the package is wrapped, a first lap of film is wrapped over the anvil, and thereafter a jaw of the clamp is moved into position adjacent the anvil for a second lap of film to be wound over the anvil and jaw. Subsequently, the heat sealer is activated and cooperates with the anvil to seal the two film laps together, and a second clamp jaw is positioned over the last lap of film to clamp the film together prior to cutting and clamping after completion of the sealing cycle. This clamping apparatus is mounted on the rotating table and requires the package to be in position for location of the anvil against the package or charge for operation of the heating and sealing apparatus. The heat is applied on the external face of the overlapped wraps between the anvil and heat assembly.
The above heating and sealing operations as well as the stapling operations require roping techniques, that is agglomerating or bunching a web of stretch film or film wrap to produce an elongated rope-like element. This roping action is taught in the above-noted apparatus and a further exemplary illustration of such roping is provided in U.S. Pat. No. 4,845,920.
The above-noted wrapping and sealing operations either utilize mechanical apparatus to seal the film to a pallet, or utilize a sealing and clamping apparatus associated with a rotatable table rather than a stationary apparatus remotely displaced and operable to the package. In the earlier application, heat is applied through the outer layer, away from the weldment interface and thus the plastic welding is not as readily controllable.